Mars Echoes of Earthtones

The path of Spirit along the floor Gusev Crater to Columbia Hills as seen by the navigation camera Credit: NASA/JPL

This banner image shows Mars at Gusev Crater in approximately true color, as if one were standing beneath the hills called Columbia.

The Spirit rover is at the base of the "West Spur" portion of the "Columbia Hills." To see Mars in its rusty, red tones with an almost olive colored sky gives a stark relief from the flat plains around the enormous crater. The hills are thought to be an older rock unit compared to what has been seen so far along the crater floor. Scientists would like to understand better the past environment at Gusev Crater and have a strategy directed towards identifying what might have been once an ancient, dry lake bed.

For Spirit to get to Columbia Hills, rover drivers have had to maneuver nearly 2 kilometers (approximately 1 mile) across often rugged terrain. The trip has taken them over a month of road work, but the plucky rover has now begun its investigations of rock layers that can only be revealed by the sharper vertical faces.

When examining the age of materials on another planet, the scientists cannot access all the tools that geologists might employ on Earth. Isotope dating of key elements, for instance, often can give a rock’s age, but the logistics of carrying isotope measuring instruments to Mars has not been completely outfitted. Instead, scientists look at the layers, since older material is buried typically underneath younger layers. As one might expect, the youngest material on top was likely deposited most recently and thus finding the older rocks takes navigational ingenuity to arrive at such valuable and exposed antiquities.

Using its rock abrasion tool, otherwise known as "Rat," both of NASA’s Mars Exploration Rovers have dotted the slopes they find to give scientists a glimpse into Mars’ layered geologic history. The rovers can also trench to depths of about six inches by locking five out of six wheels so that the chassis remains stationary and the remaining rotation of one wheel can dig. The depths reachable by this trenching technique however are limited to about one wheel radius before the axle begins to interfere.

Mission planners currently hope to drive Spirit up the peak known as West Spur after they discover what might be the most energy-efficient path to summit.